BackedBy is a protocol designed to enable monthly subscriptions between creators and their supporters, but it can be extended for any recurring monthly payment purpose. The smart contracts powering this protocol are non-upgradable, extensible, and composable. You can find them at the following addresses:
gas oracle https://polygonscan.com/address/0xce73af240eB43bBbf16223D206400F0602fb1b70
The contracts have been audited by Certik, a leading authority in blockchain security audits and the results can be found at https://www.certik.com/projects/backedby.
The UX layer at backed.by is developed separately and provides the best possible experience for the monthly subscription contract listed above. Including encryption via the Lit Protocol, and Web2 features like user administration, profile management, billing, and notifications. However, the contracts are public and any platform or integration can be built around them.